As R-Zero and I are frequently brainstorming things for Orsinium, I thought it would be a good idea to post them in the High Rock forums, as Orsinium and the Wrothgarian Mountains are part of High Rock.
Below I will submit (lore)books, that have mostly to do with Orsinium, it being culture, flora, fauna or otherwise, and there will probably be some general High Rock literature aswell.

Vilebark, the ideal poison by Nurrelon Galandris
Vilebark is a name not recognized by most. It is a rare and exotic tree found only in the Wrothgarian mountains, home to the city of Orsinium, and its inhabitants, the Orsimer.
Most are unaware of the existence of this tree, but its influence is to be found all over Tamriel. Many alchemists, including me and my associate Sinderion are in agreement, that it is one of the most potent, if not the most potent poison known to Men and Mer. When this tree exactly came to exist is unknown, due to records of varying herbalists and alchemists who have studied the surrounding region extensively, not having any information on the Vilebark whatsoever.
Though I would assure you that we already expected this, as our own research has led us to the same result. After the field expedition, many of my apprentices had perished because of the Vilebarks strong poison, and those who were in close proximity were left with severe chronic respiratory issues. The nearby Orc hunters were quick to act however, helping to carry the diseased apprentices out of the Vilebarks vicinity, and these hunters, to my surprise, were not affected by its harmful effects, except for reddening of the eyes.
Though this setback had cost us dearly, we were close to uncovering of the secret of the Vilebark tree, me and my apprentices were led deep through the mountain passes, to arrive at the home of their wise woman, who called herself Amidra-gra-Niguul. After helping my apprentices with a tonic (from which she wouldn’t disclose the ingredients), she told us that we were lucky, but that she was exceptionally lucky. She told us the most remarkable stories, and was incredibly kind. She said I could include a few of these in my report, as such I will hold me to this promise.
The origin of the Vilebark is somewhat debatable, though the story she was taught, was the legend of the blighter: “A blighter came to these lands, one of those cursed Mogoi-Khan, and wearily sat under a tree. The tree then was colossal, and bountiful of the most rich and coloured fruit, one of the fruit fell on the Mogoi-Khan. The Mogoi-Khan was angered and cursed the heavens, and out came the sour rain. The tree wouldn’t not budge and not wilt, the blighter was maddened that a mere tree could stand against his powers to control the heavens. The Mogoi-Khan spat with his cursed language, he knew the tree was strong and would not budge to a power greater than it. So he screamed the cursed words from the top of his lungs, that it became as vile as he.”
She explained that the Vilebark tree is used in many ways, the bark itself is used for medicinal purposes as a sedative, it can help numb the pain from wounds, can numb weary muscles( this is why it is sometimes used on a bow, a bow created with this bark has a stronger effect), and issometimes used recreationally, although she said that this is strongly inadvisable, as in high doses it can cause severe headaches and sometimes moments of paralysis. The leaves are more of a threat, it causes respiratory issues( similar to that which had afflicted my apprentices), severe irritation on the skin, and sometimes mucoidal thickening, which can lead to death.
But the most poisonous? She said, was the sap, which looked like a dark green ichor. Taking just a drop, or even inhale the vapor could lead to premature death, therefore it is only harvested by people who know how to deal with it, like hunters, shamans, or wise-woman like herself. She also added that the poison was best used for hunting, as it could be boiled out of the flesh.
We were surprised by the amount of knowledge Amidra-gra-Niguul had shared with us, but her reasoning to do so was justified. She said she was the last of her clan. Her clan had sought the tree to cure the bloody curse, and somehow, by Malacath’s grace she had survived. Granting her, her name Amidra-gra-Niguul, which means life’s grace in Orsimer tongue, how she had survived she didn’t want to disclose however.
After this journey, me and my apprentices gained a lot of respect for the Orsimer, for their(albeit sometimes barbaric) way of life. It had given us a lot of knowledge and wisdom, but it had also cost us dearly. Therefore reader, I ask you one thing, take this knowledge as you will, but unless you are a most experienced alchemist, do not venture out to find the Vilebark, it is the most potent poison on Tamriel.

A dragonling might you say, that is no evil and mighty dragon. Something that one could easily slay with a hunting knife. But do not! Though dragonlings are smaller than their dragon counterparts they are especially dangerous and malicious. Not only do they possess the same fire breathing capabilities as that of their larger cousins, they also speak the tongue of the snakes, a very powerful ability indeed. Already we’ve had received reports of multiple accounts of arson, and death by incineration, even children poking a dragonling multiple times with a stick! If you have a dragonling problem, ask the local guardsmen instead, they will ensure that capable warriors are hired for the proper disposal of the dragonling.

Orc Pantheon
The first and foremost figure that is revered is Malacath or Trinimac also known as the Ancestor Spirit. Trinimac is not the only one revered however, there are other spirits who can grant their boon to the Orsimer they meet, or a curse depending.
The warrior spirit – The warrior spirit is revered to as one, but consists out of many spirits, they consist out of many companions and opponents Malacath/Trinimac find worthy of reverence, most notably are the following:

Mehrunes Dagon, also known as the unstoppable rage, the Beserk, seen as a strong, but flawed and misguided rage by Malacath/Trinimac, a strong and formidable foe.
Zenithar, also known as Zhanat in Orsimer tongue, Spirit of the anvil, the forge, the armor and the weaponry, a good companion to have, as strong armor and steel is always needed. A fight blessed by Zhanat ensures victory.

Hircine, also known as Irsin or Irsine in Orsimer tongue, is the Spirit of the Hunt, depicted as a female centaur hunter with white fur, Irsin(e) is known to bring plentiful food and bounty to those that are blessed by her, but also obsesses the blessed with the Hunt, if this wildness goes on for too long the Orsimer are turned into Irsin(e)’s servants. Irsin(e) is known to both gift favour as a Warrior spirit and spirit of the Hunt and is also sometimes associated with The Lost Spirit.

Molag-Bal, also known as Molog in Orsimer tongue, is the Spirit of Greed, Molog resembles a chief that has kept power for too long and covets more, the craving to want more is what makes This spirit a dangerous opponent.

Sheogorath, also known as Galag in Orsimer tongue, or Spirit of the Unruly, Galag is sometimes represented as the impatience and eagerness for battle, Galag is the most unpredictable opponent. How the name Galag came to be is unkown, the most accepted theory is that Malacath once battled the Spirit calling him Jyg-Galag.

Torug, also known as King under Kings, or the Khan spirit, Torug is the creator of first Orsinium, through battle and hardship did this Orsimer claims his side by Malacath/Trinimac as a worthy companion. Among the Warrior Spirit, Torug is the one they seek most.

Trinimac and Malacath aren't the same, even if one is supposedly created from the other. Saying this would be highly offensive to a follower of either.

While well written, I don't see this as the Orc pantheon. I agree that Torug is probably revered, but the Orcish people are really unique in Tamriel in that they follow one god - their outcast pariah god Malacath (recent Trinimac controversy being a new thing altogether). While there are numerous Orcs following other Daedras, I don't think it's fitting that they're considered almost equals to Malacath or even in the same group. Trinimac worshippers would probably distance themselves from Daedra as much as possible.

I should really change the text to either contain Malacath or Trinimac, though I wanted to keep it both in for now and is not final. Malacath/Trinimac is revered first and foremost and is seen as the ancestor spirit, the strongest and most powerful, and sometimes not even associated with the spirits, except for Auri-El( From a part that still has to be written). Though I would think it's a bit weird if they were complete oblivious of other strongly influential beings except for Trinimac/Malacath, influencing them more as spirits, or simply not seen as gods, but as impactful beings, and depending on the situation are revered for the charms they give( Irsin(e) for example could bless a hunt to go well) or shunned for the curses they bring(Galag bringing an Orc to a craze) and can either be seen as good or evil, depending on the situation(Except for The Betrayers, which are regarded as always evil, again a piece I have not written yet). The spirits are in turn divided how Malacath/Trinimac sees them, the warrior spirit explained above is one such example, a cumulation of different spirits that could help in battle, often asked for a blessing as one, though they are sometimes called upon individually(Zhanat would probably be called on by a smith, while Torug would be called for by a warrior), The spirits are influential beings that are not the benevolent, omniscient, omnipotent, omnipresent, righteous, merciful god that is Trinimac/Malacath

I didn't mean that they aren't aware of other divine beings, but that they do not worship them. Like pariahs they follow their pariah god, being outsiders and outcasts to everyone else.

Also the new Trinimac faith had huge implications. Among these are the fact that if Malacath and Trinimac aren't pre- and post-Boethiah Trinimac, then Malacath is an evil prince that has tricked the Orcs since the Dawn era. And in the Trinimac faith there's absolutely no place for Daedra worship.

In early stage development, prone to changes, worked out who's who, now it is the time to add some backstory, which I will post later.

Orc Pantheon

The first and foremost figure that is revered is Malacath or Trinimac also known as the Ancestor Spirit.(Depending on views if it comes from either a Malacath or a Trinimac cultist, I leave this open as a general interpretation that is rooted in Orsimer culture that both sides (mostly) agree on).

Trinimac is not the only one present however, there are spirits who can grant their boon to the Orsimer they meet, or a curse depending.

The warrior spirit – The warrior spirit is revered to as one, but consists out of many spirits, they consist out of many companions and opponents Malacath/Trinimac find worthy of reverence, most notably are the following:

Mehrunes Dagon, also known as Mehron in Orsimer tongue, the unstoppable rage, the Berserk, seen as a strong, but flawed and misguided rage by Malacath/Trinimac, a strong and formidable foe.

Zenithar, also known as Zhanat in Orsimer tongue, Spirit of the anvil, the forge, the armor and the weaponry, a good companion to have, as strong armor and steel is always needed. A fight blessed by Zhanat ensures victory.

Hircine, also known as Irsin or Irsine in Orsimer tongue, is the Spirit of the Hunt, depicted as a female centaur hunter with white fur, Irsin(e) is known to bring plentiful food and bounty to those that are blessed by her, but also obsesses the blessed with the Hunt, if this wildness goes on for too long the Orsimer are turned into Irsin(e)’s servants. Irsin(e) is known to both gift favour as a Warrior spirit and spirit of the Hunt and is also sometimes associated with The Lost Spirit.

Molag-Bal, also known as Molog in Orsimer tongue, is the Spirit of Greed, Molog resembles a chief that has kept power for too long and covets more, the craving to want more is what makes This spirit a dangerous opponent. Depicted as a large elf, that has Orsimer on chains.

Sheogorath, also known as Galag in Orsimer tongue, or Galag’al in Old Orcish, Spirit of the Unruly, Galag is sometimes represented as the impatience and eagerness for battle, Galag is the most unpredictable opponent. How the name Galag came to be is unknown, the most accepted theory is that Malacath once battled the Spirit calling him Jyg-Galag. Portrayed as a woman like figure, cloaked by vibrant robes and a silver mask.

Torug, also known as King under Kings, or the Khan spirit, Torug is the creator of first Orsinium, through battle and hardship did this Orsimer claims his side by Malacath/Trinimac as a worthy companion. Among the Warrior Spirit, Torug is the one they seek most.

Namira, also known as Namara, the Spirit of Wicked Nature, she represents nature in the Wrothgarian Mountains,

Auri-El, also known as Urvash, or Urvash’al in old Orcish, Spirit of Time, normally mentioned as The Betrayer.
Most if not all Orsimer know the story of The Betrayer, Urvash’al, brother to Trinimac and leader of most known pantheons to date, but this was not always the case. Trinimac was the champion of his people, sometimes revered more than Urvash’al. Urvash’al grew jealous, jealous that his brother was more liked than he, this consumed Urvash’al. When the time came, when Trinimac was consumed by the evil Bidesha, tortured and beaten, Urvash’al ignored Trinimac, neglected Trinimac, and watched his own brother transform in the spawn that is called Mauloch. He betrayed Trinimac and thus the Orsimer, granting him the title of Betrayer.

Mephala, also known as Mefar or Mafar, Spirit of Rebirth,
Boethiah, also known as Bidesha, Spirit of Torment,

Peryite, also known as Hulmog, The Fallen Serpent,
Hermaous Mora, also known as Harmos, or Harmaros in old Orcish, Spirit of Secrets
Vaermina, also known as Urma, Spirit of Delusions, , portrayed as a shapeshifter consisting of dark black form.(Aku from Samurai jack )

Clavicus Vile, also known as Klavil, or Khlav’ig in old Orcish, Spirit of Desire, has the appearance of a rich Breton lord with Klavil’s mask
Nocturnal, also known as Noktur or Noktul, Spirit of Shadow,
Azura, also known as Azug, or Ashara, Spirit of the Moon, depicted as a meditating man in blue silks, holding up the moon(s), appears before those whom are in senses with their higher self.
Sanguine, also known as Sanhk, or Sanhku’in in old Orcish, Spirit of Bloodshed/Dark Intent
Meridia, also known as (Meritah?), Spirit of Light
Magnus, also known as Magkne, Spirit of Elements, seen as the origin of (raw) elemental power
Julianos, also known as, Ghulan, Spirit of Knowledge,
Mara, Spirit of Care
Arkay, also known as Urkhai(LOTR reference ), Spirit of Passing, also called The Gatekeeper, when an Orsimer dies, this spirit will test the strength of Orcs ,
Stendarr, also known as Mogohk, meaning “Shield of the Serpent”, Spirit of Loyalty, generally depicted as a man only holding a shield,
Lorkhan/Shor/Ysmir, also known as Mogosh, meaning “Serpent King”, The spirit of Lies, generally seen as half-serpent, half-man. The battles between Malacath and Mogosh are legendary.
Kynareth, also known as Kyn, or Kyn’eh in old Orcish, Life Spirit,
Talos does not appear in the Orcish pantheon.
Dibella does not appear in the Orcish pantheon.

One spirit, consisting of three Altmer gods, the three faced god, Yafarn/Yfran, The Spirit of Wisdom, Legacy and Magic.
Yfran was once three gods:
Y’ffre, also known as Yafr/Ifrey
Phynaster, also known as Fynast
Syrabane, also known as Khyraban

King Bormic sat on his prestigious throne, hearing the pleas of his most trusted knights, that failed to give him what he had desired.
His words instilled fear, for he who wronged our merciful king, shan't live for another year.
“You have come to me empty-handed”, said his booming voice that broke branches and ringed ears. “I asked for a trophy unrivalled, and you brought me the head of a deer!”
“It wasn’t me!” screamed Adwen, lord of hills and hovels, slayer of boars and parakeet. “I hunted down Great-Tusk for you my liege, with his meat we could feast for weeks.”
“Then why is my plate still empty”, Bormic bellowed. Why haven’t you killed that boar, answer me, or I will eat all of you whole!”

“The fool can’t hit anything with his bow”. Answered Celoranne, queen of fishes and boats. His shots missed the mark, and Great-Tusk fled.

A soul, willing. A mare slaughtered.
Lay him on a bed of flowers, keep still.
Stone, hard as earth. Sisters, pick one.
Crush it, keep hitting until it cracks, like hen’s egg.
Lay his dreams open to the wind, let nature take them.
Let fungus rot, dreams turn to nightmares.
Take nature made into tool, let flesh rip like bone cracked.
Let him spill, let flowers bloom crimson red.
Take tendon and sinew, braid with twigs, thorns and hair of witch.
Take flesh and everything left inside, light cauldron’s fire.
Boil with mare’s blood, let man and beast become one.
Sisters, each take our copper cup.
Let the broth fill it to the brim, let it fill our mouths.
Let it drip from the mouth, let us laugh in cacophony.
Let it fill our hearts, one with nature, throbbing.

All turns to dust, or naught more than dust.
All-eater worm eats all that is, excretes all that was, and eats all again. Like small worm eat bread until only crumbs remain.

This is the inevitability of all things that follow The Way that Winds.
Like maggots it eats flesh.
On wood like termites it munches.

But like many things float in the river, others sink.
Copper and brass does not float, otherwise how would sunken-head bestow his wisdom upon us?
Likewise bone sinks to the bottom of the earth, but unlike brass collapses under the torrent, disintegrating into plant.

We have the gift to see all that flows, has passed the waters of now, and where it will flow. As we know, water in a river takes the easiest path, and so does The Way That Winds.

The ripples in the water or the wave which crashes against rocks on shore, is nothing short of physical manifestation of spirits. Those foolish to move against the current. In the reflection of The Way That Winds that we see upon us.

These are ignorant and cling to what they were, what was once. Desperate to fight for their integrity, to be whole and full. While the wise among them can see the irreversible path, and guided by providence, steer their way into larger waters. For all cannot be eternal, and must change, as all-eater-worm breaks down all.

The Way that Winds - The way of mortal life, all spirits, alive and passing to the next follow The Way that Winds. The Way that Winds is symbolized by a stream of water flowing in only one direction, though the Way that Winds has many streams, the only one path is forward. Water is the connection between the spirit world and the materialistic world.

All-Eater Worm - The way in which everything degrades and becomes nothing, or next to nothing. All-Eater worm devours all Mortal Spirits that pass through his mouth, and excretes them as spirits lesser than that they were. All-Eater worm stands for degradation, permanent death, and oblivion.

The Abyss - The Abyss or 'The Deep Ways' are a complex series of caves that connect the divine 'inner' to the mortal cycle, mortals, except highly gifted Bjoulsae sages, are unable to pass into it's streams. The Abyss is home to a mystical figure called Sunken-Head. It is said that mountains and glaciers are connect the Abyss to the mortal plane.

The Inner - The Inner or 'Everlasting Spring' is a place that mortals have never seen, but has found its way into the concept through the old stories told by Watermanes. It speaks of a neverending stream of water that supplies water to The Abyss and the Mortal cycle, the water also streams into The Void.

The Void - The Void is an empty space that is positioned in the middle of the Divine Cycle. The believe exists that the mortal spirits were created by revolvement of the wheel, ousting of Divine Spirits, that degraded in All-Eater worm. The Bjoulsae Tribes believe that if there ever comes a time the Cycle will start to revolve again, everything will degrade, Divine turns into Mortal again, and all that was turns into dust once more.

Classification of spirits (abbreviated):

Mortal Spirits - Mortal Spirits are defined by their involvement in the outer wheel, or the Mortal Cycle. They are degraded into lesser spirits by All-Eater worm.

Sunken Head -Sunken Head is an ancient wise sage, that by his knowledge sunk into The Abyss, and is one of the few mortals to ever touch the Abyss. His words are carried along the streams of the mortal cycle.

Divine Spirits - The Divine Spirits live inside the Divine Cycle and, they're in the eyes of the Bjoulsae Tribes immortal and unreachable. The only connection the Bjoulsae Tribes and Divine Spirits have is through the Watermanes. Divine Spirits sometimes bring gifts down The Abyss for mortals.

Watermanes - Watermanes are the only spirits that can traverse The Abyss to the Mortal and Divine Cycles. They offer guidance to mortals, and bring messages between the planes. It is said that horses stem from noble mortal spirits that have traversed the Divine Cycle.